(1) Field of the Invention
This invention relates to the preparation of a bioadhesive composition from the coproduct/byproduct of the dry milling corn ethanol industry e.g. distillers' dried grains with solubles (DDGS). The DDGS was treated with a strong aqueous alkali solution, with or without urea, filtered to remove insolubles and then concentrated by removing water to obtain a bioadhesive. The percent DDGS that can go into making the bioadhesive system is high. This bioadhesive composition shown in FIG. 1 has the strength to bind paperboard and corrugated paperboard. The DDGS-based bioadhesive applied to a corrugated paperboard is shown in FIG. 2. The bioadhesive composition has a high solid content and a low Brookfield viscosity, which is an advantage for paperboard binding.
(2) Description of the Related Art
Corn based ethanol industries are growing at a very fast rate in the United States. The two methods adopted in making bioethanol from corn are: dry milling and wet milling. In the United States, there are a larger number of the dry milling than the wet milling industries. Distillers' dried grains with solubles (DDGS) are the coproducts from the dry milling corn ethanol industries. The byproducts/coproducts of corn-based ethanol industries mostly go for low cost animal feeds.
Traditionally, starch is one of the main raw materials for preparing bioadhesive that is mainly used for binding papers or corrugated paperboards (U.S. Pat. No. 5,096,491 to Nagai et al; and U.S. Pat. No. 6,716,280 to Atkinson). Soy protein isolate-based adhesives had been studied (Zhong, Z. K., Sun, X. S., Fang, X. H., Ratto, J. A., Int. J. Adhesion and Adhesives 2002, 22 (4) pages 267-272; and Li, K. C., Peshkova, S., Geng, X. L., J. Am. Oil Chem. Soc. 2004, 81 (5) pages 487-491). U.S. Pat. No. 7,081,159 to Thames et al describes mixed water; zinc, soy protein or flour, strong base, such as sodium benzoate or sodium hydroxide, to prepare a bioadhesive by cooking processing. Urea, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, and guanidine hydrochloride were used by Sun et al (U.S. Pat. No. 6,497,760) to modify soy protein isolate for preparing protein-based adhesive. Soy protein isolate powder, NaOH and water were mixed followed by cooking to hydrolyze protein in preparing protein-based adhesive. These adhesives were used for bonding lignocellulosic composites (U.S. Pat. No. 7,060,798 to Li et al). Sodium hydroxide and urea are known for carrying out the destructurization of proteins (Cheng, E., Sun, X., Karr, G. S., Composites Part A: Applied Science and Manufacturing, 2004, (35) pages 297-302).